//
// experimental/impl/promise.hpp
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2021-2022 Klemens D. Morgenstern
//                         (klemens dot morgenstern at gmx dot net)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#ifndef ASIO_EXPERIMENTAL_IMPL_PROMISE_HPP
#define ASIO_EXPERIMENTAL_IMPL_PROMISE_HPP

#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)

#include "asio/cancellation_signal.hpp"
#include "asio/experimental/detail/completion_handler_erasure.hpp"
#include <tuple>
#include <optional>

#include "asio/detail/push_options.hpp"

namespace asio {
    namespace experimental {

        template<typename Signature = void(), typename Executor = any_io_executor>
        struct promise;

        namespace detail {

            template<typename Signature, typename Executor>
            struct promise_impl;

            template<typename ... Ts, typename Executor>
            struct promise_impl<void(Ts...), Executor> {
                using result_type = std::tuple<Ts...>;

                promise_impl(Executor executor = {})
                        : executor(std::move(executor)) {
                }

                std::optional <result_type> result;
                bool done{false};
                detail::completion_handler_erasure<void(Ts...), Executor> completion;
                cancellation_signal cancel;
                Executor executor;
            };

            template<typename Signature = void(), typename Executor = any_io_executor>
            struct promise_handler;

            template<typename Signature, typename Executor>
            struct promise_handler;

            template<typename ... Ts, typename Executor>
            struct promise_handler<void(Ts...), Executor> {
                using promise_type = promise<void(Ts...), Executor>;

                promise_handler(Executor executor) // get_associated_allocator(exec)
                        : impl_{
                        std::allocate_shared<promise_impl<void(Ts...), Executor>>(
                                get_associated_allocator(executor))} {
                    impl_->executor = std::move(executor);
                }

                std::shared_ptr <promise_impl<void(Ts...), Executor>> impl_;

                using cancellation_slot_type = cancellation_slot;

                cancellation_slot_type get_cancellation_slot() const

                noexcept
                {
                    return impl_->cancel.slot();
                }

                auto make_promise() -> promise<void(Ts...), Executor> {
                    return {impl_};
                }

                void operator()(std::remove_reference_t <Ts>... ts) {
                    assert(impl_);
                    impl_->result.emplace(std::move(ts)...);
                    impl_->done = true;
                    if (auto f = std::exchange(impl_->completion, nullptr); f != nullptr)
                        std::apply(std::move(f), std::move(*impl_->result));
                }
            };

        } // namespace detail
    } // namespace experimental
} // namespace asio

#include "asio/detail/pop_options.hpp"

#endif // ASIO_EXPERIMENTAL_IMPL_PROMISE_HPP
